Re: Topband: Broadband Inverted L
It sure IS broadbanded. Couple of questions: On Thu, Nov 20, 2014 at 10:11 AM, Joe Galicic gali...@comcast.net wrote: The ground is connected to the existing ground system for the old L. Can you describe this? I get a 1.1 SWR reading from 1.8 to 1.9 before it moves up to 1.3 and slightly higher to 2.0. The antenna seems to be working OK (relative to the old L). This seems awfully broad banded? Where are you measuring the SWR? At the feedpoint or at the end of the 125' coax? 73, Mike www.w0btu.com _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Broadband Inverted L
Mike, The antenna feed point terminates at a four foot ground rod and then I am running a number 14 wire from that ground rod to my existing radial field. That run is about 40 feet. The radial field consists of 3 8 foot ground rods and nearly 2000 feet of wire spread out over my entire front and back yard. I didn’t want to run new radials over top of the existing so that's why I did what I did. I am measuring SWR from the shack end of the feed line. My old L was only 35 foot vertical. I thought 65 foot vertical would be much better but sometimes the old L hears and transmits better by a couple S units depending on where the station is of course. So I think something is off? Hopefully I didn’t build myself an accidental dummy load? -Joe - Original Message - From: Mike Waters mikew...@gmail.com To: Joe Galicic gali...@comcast.net Cc: List, TopBand topband@contesting.com Sent: Thursday, November 20, 2014 11:17:16 AM Subject: Re: Topband: Broadband Inverted L It sure IS broadbanded. Couple of questions: On Thu, Nov 20, 2014 at 10:11 AM, Joe Galicic gali...@comcast.net wrote: The ground is connected to the existing ground system for the old L. Can you describe this? blockquote I get a 1.1 SWR reading from 1.8 to 1.9 before it moves up to 1.3 and slightly higher to 2.0. The antenna seems to be working OK (relative to the old L). This seems awfully broad banded? /blockquote Where are you measuring the SWR? At the feedpoint or at the end of the 125' coax? 73, Mike www.w0btu.com _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Broadband Inverted L
Joe: Don't ask questions and just enjoy the antenna's performance. 73 de Gene Smar AD3F On 11/20/14, Joe Galicic wrote: I moved my 160 inverted L to a tall tree in my backyard to get more vertical height. The vertical leg is now about 65 feet and the rest (65feet) is horizontal. I fed this one with about 125 feet of 75 ohm coax just because I had lots of it laying around. No tuners, baluns, ununs or chokes in the feed line. The ground is connected to the existing ground system for the old L. I get a 1.1 SWR reading from 1.8 to 1.9 before it moves up to 1.3 and slightly higher to 2.0. The antenna seems to be working OK (relative to the old L). This seems awfully broad banded? Any feedback would be great. Thanks -Joe N3HEE _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Broadband Inverted L
In my case, I started out with four radials, great wideband match ~100KHz When I had some more time and wire, I went to 8 radials, that cut the bandwidth in half, still a good match. Each chance I had to add more radials, I did. Each time the bandwidth decreased substantially, but the antenna kept working better with more radials as measured by my success working weaker and more distant stations. I'm up to 60 radials now, antenna is no longer wideband, but works better than ever. I figured out that I was cooking dirt back in the days that I had only a few radials. Now it requires a tuner to QSY more that 10 KHz, but again it works so much better. Examples, 160m worked and confirmed this year, W1AW in all 50 states, Amsterdam Is, Lord Howe Is, S. Cook Is. I suggest adding ground radials or a ground screen around the new feed point - as close to the surface as possible, and attach to the previous ground system too. 73 Lloyd - N9LB -Original Message- From: Topband [mailto:topband-boun...@contesting.com]On Behalf Of Joe Galicic Sent: Thursday, November 20, 2014 11:11 AM To: Mike Waters Cc: List, TopBand Subject: Re: Topband: Broadband Inverted L Mike, The antenna feed point terminates at a four foot ground rod and then I am running a number 14 wire from that ground rod to my existing radial field. That run is about 40 feet. The radial field consists of 3 8 foot ground rods and nearly 2000 feet of wire spread out over my entire front and back yard. I didn’t want to run new radials over top of the existing so that's why I did what I did. I am measuring SWR from the shack end of the feed line. My old L was only 35 foot vertical. I thought 65 foot vertical would be much better but sometimes the old L hears and transmits better by a couple S units depending on where the station is of course. So I think something is off? Hopefully I didn’t build myself an accidental dummy load? -Joe - Original Message - From: Mike Waters mikew...@gmail.com To: Joe Galicic gali...@comcast.net Cc: List, TopBand topband@contesting.com Sent: Thursday, November 20, 2014 11:17:16 AM Subject: Re: Topband: Broadband Inverted L It sure IS broadbanded. Couple of questions: On Thu, Nov 20, 2014 at 10:11 AM, Joe Galicic gali...@comcast.net wrote: The ground is connected to the existing ground system for the old L. Can you describe this? blockquote I get a 1.1 SWR reading from 1.8 to 1.9 before it moves up to 1.3 and slightly higher to 2.0. The antenna seems to be working OK (relative to the old L). This seems awfully broad banded? /blockquote Where are you measuring the SWR? At the feedpoint or at the end of the 125' coax? 73, Mike www.w0btu.com _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Broadband Inverted L
On Thu,11/20/2014 9:25 AM, Gene Smar wrote: Don't ask questions and just enjoy the antenna's performance. A low SWR is NOT an indicator of an antenna's performance. It only indicates a match to the transmission line. In this case, the low SWR suggests that the antenna is highly resistive. The radiation resistance of an antenna of that height is less than ten Ohms. The rest of the 70 ohms or so of resistance it takes to produce that nice match is LOSS -- a bit in the wire resistance, the rest of it in the radial system. A connection to earth is NOT an efficient part of an antenna -- the earth is lossy (a big resistor). The only reason for having a driven rod is for lightning protection. It's those radials that are providing a return for antenna current, and 2,000 ft of wire is not a lot on 160M. Over average soil, 2000 ft of wire typically provides a ground loss resistance on the order of 10 ohms; over poor soil, the loss resistance will be higher, over good soil, it will be less. The high value of loss suggests that perhaps your radials might not be making a good connection to the coax shield, so all the antenna sees is those driven rods. To understand this, and for some practical ideas for radial systems, study http://k9yc.com/160MPacificon.pdf 73, Jim K9YC _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Broadband Inverted L
Joe posted, I moved my 160 inverted L to a tall tree in my backyard to get more vertical height. The vertical leg is now about 65 feet and the rest (65feet) is horizontal. I fed this one with about 125 feet of 75 ohm coax just because I had lots of it laying around. No tuners, baluns, ununs or chokes in the feed line. The ground is connected to the existing ground system for the old L. I get a 1.1 SWR reading from 1.8 to 1.9 before it moves up to 1.3 and slightly higher to 2.0. The antenna seems to be working OK (relative to the old L). This seems awfully broad banded? Any feedback would be great. Thanks -Joe N3HEE and Joe added: The antenna feed point terminates at a four foot ground rod and then I am running a number 14 wire from that ground rod to my existing radial field. That run is about 40 feet. The radial field consists of 3 8 foot ground rods and nearly 2000 feet of wire spread out over my entire front and back yard. I didn't want to run new radials over top of the existing so that's why I did what I did. I am measuring SWR from the shack end of the feed line Unfortunately there is almost no radial system ground connection at all on the new inverted L, because there is almost 1/8th wave of a single thin wire between the real ground and the feedpoint. That wire length, 40 ft, could add hundreds of ohms impedance to the ground path. While bandwidth is a terrible way to guess efficiency, it is also obvious the ground radial connection really isn't a worthwhile connection at all. 73 Tom _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Broadband Inverted L
Have you considered elevated radials? Four of them 10' high (or even two!) would be MUCH better than what you have right now. My 160m Inverted-L: http://www.w0btu.com/160_meters.html#inv-l_antenna 73, Mike www.w0btu.com _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Broadband Inverted L
Thanks everyone ! Interesting. I knew something was not quite right. I thought I could tap into the existing ground system but obviously that is not going to be the case. I could manage two elevated radials pretty easily but not at 10 ten feet. More like 6 feet off the ground mounted on my 6 foot high wooden privacy fence. Can I lay down radials more over top of the old ones? - Original Message - From: Mike Waters mikew...@gmail.com To: List, TopBand topband@contesting.com Sent: Thursday, November 20, 2014 1:23:32 PM Subject: Re: Topband: Broadband Inverted L Have you considered elevated radials? Four of them 10' high (or even two!) would be MUCH better than what you have right now. My 160m Inverted-L: http://www.w0btu.com/160_meters.html#inv-l_antenna 73, Mike www.w0btu.com _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Broadband Inverted L
I suppose another question is this all worth it? Meaning, is the L with 65 foot vertical leg with proper ground going to greatly outperform the L with 35 foot vertical leg ? - Original Message - From: Joe Galicic gali...@comcast.net To: Mike Waters mikew...@gmail.com Cc: List, TopBand topband@contesting.com Sent: Thursday, November 20, 2014 2:12:28 PM Subject: Re: Topband: Broadband Inverted L Thanks everyone ! Interesting. I knew something was not quite right. I thought I could tap into the existing ground system but obviously that is not going to be the case. I could manage two elevated radials pretty easily but not at 10 ten feet. More like 6 feet off the ground mounted on my 6 foot high wooden privacy fence. Can I lay down radials more over top of the old ones? - Original Message - From: Mike Waters mikew...@gmail.com To: List, TopBand topband@contesting.com Sent: Thursday, November 20, 2014 1:23:32 PM Subject: Re: Topband: Broadband Inverted L Have you considered elevated radials? Four of them 10' high (or even two!) would be MUCH better than what you have right now. My 160m Inverted-L: http://www.w0btu.com/160_meters.html#inv-l_antenna 73, Mike www.w0btu.com _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Broadband Inverted L
Ground systems cannot be evaluated or estimated by number of feet of wire, just like they cannot be evaluated by SWR or bandwidth, but I'm sure we all agree on this.. The single most important thing Joe said was: The antenna feed point terminates at a four foot ground rod and then I am running a number 14 wire from that ground rod to my existing radial field. That run is about 40 feet. Joes has virtually no ground at all on 160 meters, because his system's ground connection to the radials is via a single #14 wire 40 feet long. A 40 ft long wire laid on earth to the radials, even if Joe had 50 x 100 ft radials, would almost certainly make the ground path impedance hundreds of ohms. Joe's antenna virtually doesn't have a ground connection to radials at all, and this has almost nothing to do with the number of radials or type of radials. It has to do with the 40ft long connection. 73 Tom _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Broadband Inverted L
Thanks Tom. I get the picture now. Time to go out and connect more radials directly to the feed point ground. I can also elevate two of them. -Joe - Original Message - From: Tom W8JI w...@w8ji.com To: List, TopBand topband@contesting.com Sent: Thursday, November 20, 2014 2:17:55 PM Subject: Re: Topband: Broadband Inverted L Ground systems cannot be evaluated or estimated by number of feet of wire, just like they cannot be evaluated by SWR or bandwidth, but I'm sure we all agree on this.. The single most important thing Joe said was: The antenna feed point terminates at a four foot ground rod and then I am running a number 14 wire from that ground rod to my existing radial field. That run is about 40 feet. Joes has virtually no ground at all on 160 meters, because his system's ground connection to the radials is via a single #14 wire 40 feet long. A 40 ft long wire laid on earth to the radials, even if Joe had 50 x 100 ft radials, would almost certainly make the ground path impedance hundreds of ohms. Joe's antenna virtually doesn't have a ground connection to radials at all, and this has almost nothing to do with the number of radials or type of radials. It has to do with the 40ft long connection. 73 Tom _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Broadband Inverted L
Exactly what I thought ... any way to slope the leg of the L to get it at the junction of the redials? de ns9i On 11/20/2014 1:17 PM, Tom W8JI wrote: Ground systems cannot be evaluated or estimated by number of feet of wire, just like they cannot be evaluated by SWR or bandwidth, but I'm sure we all agree on this.. The single most important thing Joe said was: The antenna feed point terminates at a four foot ground rod and then I am running a number 14 wire from that ground rod to my existing radial field. That run is about 40 feet. Joes has virtually no ground at all on 160 meters, because his system's ground connection to the radials is via a single #14 wire 40 feet long. A 40 ft long wire laid on earth to the radials, even if Joe had 50 x 100 ft radials, would almost certainly make the ground path impedance hundreds of ohms. Joe's antenna virtually doesn't have a ground connection to radials at all, and this has almost nothing to do with the number of radials or type of radials. It has to do with the 40ft long connection. 73 Tom _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Broadband Inverted L
On Thu,11/20/2014 11:17 AM, Tom W8JI wrote: Joe's antenna virtually doesn't have a ground connection to radials at all, and this has almost nothing to do with the number of radials or type of radials. Yes, but there's another important concept that is being missed here. The function of a radial system is NOT to couple the antenna to the earth, it is to SHIELD the antenna from the earth. Rather, the function of a radial system is to serve as a return for both the antenna current AND THE FIELD produced by the antenna. That is, a good radial system acts as a SHIELD between that field and the lossy earth. Joe's system has a counterpoise (a return for the current), albeit not a good one, but it doesn't perform the shielding function because it's not just below the base of the antenna. K2AV's folded counterpoise is another example of a system that provides an effective return for antenna current, but provides much less of a shielding function. Time to go out and connect more radials directly to the feed point ground. NOT to the earth, to the coax shield. I can also elevate two of them. I suggest that you study the link I posted. N6LF has done a lot of excellent work on radial systems, much of which is summarized in that link. On 160M, radials must be at least 16 ft off the ground to work as elevated radials, and they should be of equal lengths and heights. Radials on the ground can be of any length --the only more or less universal rules of thumb is that more copper on the ground is better, and more short radials is better than a few long ones. Think of it this way -- the current in any radial must be minimum at the end, and if it's less than a quarter wave, will be maximum at the feedpoint. The antenna return current divides between the radials, and the loss is I squared R, where this R is coupled from the lossy earth. The more radials there are to divide that current, the less will be the lost power! That's because the current is divided by N (the number of radials) while the loss is divided by N squared. The reason a fewer number of elevated radials can work as well as many more on the ground is that the fields from the elevated radials don't couple as closely to the earth, so there's less coupled R, and thus less lost power. 73, Jim K9YC _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Broadband Inverted L
A few years ago I put up a temporary 60 foot vertical over my 230 foot diameter ground screen. It was top loaded with 2 umbrella wires sloping down. The bandwidth was MUCH narrower than your 65 foot vertical. IIRC, the 3:1 VSWR bandwidth was less than 50 kHz. The feedpoint impedance was about as predicted by EZNEC over a perfect ground. IE, very low. It got out really well in contests (anecdotal data). If you are seeing a bandwidth broad as a barn door, it can probably only be explained by substantial ground losses. I understand you can't get a ground like I have, do the best you can and get on the air. Rick N6RK On 11/20/2014 8:11 AM, Joe Galicic wrote: I moved my 160 inverted L to a tall tree in my backyard to get more vertical height. The vertical leg is now about 65 feet and the rest (65feet) is horizontal. I fed this one with about 125 feet of 75 ohm coax just because I had lots of it laying around. No tuners, baluns, ununs or chokes in the feed line. The ground is connected to the existing ground system for the old L. I get a 1.1 SWR reading from 1.8 to 1.9 before it moves up to 1.3 and slightly higher to 2.0. The antenna seems to be working OK (relative to the old L). This seems awfully broad banded? Any feedback would be great. Thanks -Joe N3HEE _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Broadband Inverted L
Hi, Joe I didn't have time to write you earlier. It was obvious that you had a lot of ground loss in series with the radiation resistance of the inverted-L that was swamping the reactance variation of the inverted L. You are likely to be very pleasantly surprised at how effective two elevated resonant radials at 5-6' can be! I did that for years - worked JA, VKs, VK6, JT1, S79,many deep European and Russians, lots of, LOTs of Pacific and DXpeditons etc.. Of course you can also lay out some more radials from your feed-point! Good luck! Have fun! The taller vertical section will help a lot! Mine was about 75 feet! 73, Charlie, K4OTV -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Joe Galicic Sent: Thursday, November 20, 2014 2:12 PM To: Mike Waters Cc: List, TopBand Subject: Re: Topband: Broadband Inverted L Thanks everyone ! Interesting. I knew something was not quite right. I thought I could tap into the existing ground system but obviously that is not going to be the case. I could manage two elevated radials pretty easily but not at 10 ten feet. More like 6 feet off the ground mounted on my 6 foot high wooden privacy fence. Can I lay down radials more over top of the old ones? - Original Message - From: Mike Waters mikew...@gmail.com To: List, TopBand topband@contesting.com Sent: Thursday, November 20, 2014 1:23:32 PM Subject: Re: Topband: Broadband Inverted L Have you considered elevated radials? Four of them 10' high (or even two!) would be MUCH better than what you have right now. My 160m Inverted-L: http://www.w0btu.com/160_meters.html#inv-l_antenna 73, Mike www.w0btu.com _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
